Industrial kiln and oven



B. J.-MOORE ET AL INDUSTRIAL KILN AND OVEN May 8, 1945.

Filed April 18, 1944 2 Sheets-Sheet 1 INVENTQR ORNEY.

2 Sheets-Sheet 2 y 1945- B. J. MOORE ETAL INDUSTRIAL KILN AND OVEN FiledApril 18, 1944 INVEHTOR a K; rm

A T NEW.

Wzwwww Patented May 8, 1945 INDUSTRIAL KILN AND ()VEN Bernard J. Mooreand Bernard 0. Moore, Stoke-on-Trent, England Application April 18,1944, Serial No. 531,591 In Great Britain February 5, 1943 9 Claims.(01. 13-22 This invention relates to industrial kilns and ovenshereinafter referred to and included in the term kiln and has for itsobject to provide an improved construction of kiln suitable for workingat a high temperature.

According to the present invention the kiln is provided with electricresistance heating elements formed of powdered graphite or otherelectrical conducting material contained in refractory housings, whichcomprise inner and outer refractory members spaced apart to provide acavity therebetween and refractory powder filling said cavity.

The invention is particularly applicable to a tunnel kiln and as soapplied the kiln may be provided with a plurality of the electricresistance heating elements which may be arranged substantiallytransversely to the length of the tunnel, i. e., substantiallytransversely to the direction of flow of the goods through the tunnelkiln.

Normally the heating elements would be arranged substantially verticallyand together with the refractory housings disposed in recesses providedat opposite sides of the interior of the kiln, for instance, the kilnmay be provided along its sides with a, series of spaced brickworkpillars and the heating elements are located in the spaces between thesepillars. Those faces of the pillars which are transverse to the lengthof the kiln may be provided with grooves or ribs extending from top tobottom and engaging these ribs or projecting into the grooves may beedges of refractory members in the form of plates which form the wallsof the refractory housings for receiving the powdered graphite.

Alternatively, two refractory tubes of different diameters may be usedone within the other and the intervening cavity filled with refractorypowder, the powdered graphite or other conducting material being placedwithin the doublewalled housing so formed.

Preferably the housings are elongatedin the direction of current flowand may be tapered from top to bottom so that the higher temper- Zturewill be generated towards the bottom of the iln.

In either form the cavity in the housing wall' may b packed withpowdered fused alumina, sand or any other refractory powder and therefractory members themselves may be made of fused alumina, sillimaniteor fireclay although for working at lower temperatures the members maybe made of fused quartz or silica.

Referring to the drawings-- Figure 1 is a cross sectional plan view ofone form of tunnel kiln constructed in accordance with this invention.

Figures 2 and 3 are a sectional side elevation and a plan view,respectively, of one of the heating elements of the same constructiondrawn to an enlarged scale. I

Figures 4, 5 and 6 are views corresponding with Figures 1, 2 and 3illustrating a modified construction.

Figure '7 is a cross sectional plan view of multiple tunnel kilnprovided with heating elements in accordance with this invention.

Referring to Figures 1 to 3 of the drawings the tunnel kiln thereillustrated comprises a main refractory structure I0 of known formprovided with the usually elongated heating chamber H along which thegoods are fed slowly through the kiln and on opposite sides of thechamber the main structure is provided with recesses l2 within which theheating elements are disposed.

In the construction illustrated the heating chamber is arrangedsubstantially horizontally and within the recesses 12 are arranged aplurality of spaced vertical pillars l3 of brickwork or other suitablerefractory material. Between opposite faces of adjacent pillars extendvertical refractory walls l8 which are spaced apart to provide, inconjunction with the surfaces of the pillars, a housing for powderedconducting material [9.

The refractory walls 18, shown solid for convenience in Figure 1, areillustratedin detail in Figures 2 and 3, from which it will be seen thateach comprises spaced outer and inner portions !5, ll built. up of flatrefractory plates placed vertically edge to edge, the cavity l6 betweenthem being packed with a suitable refractory powder, such as fusedalumina.

The material l9 forming the core of the heating element is preferablypowdered graphite but other conducting materials may be used such, forinstance, as other forms of carbon or carborundum.

The refractory housing of each heating element extends from the upper tothe lower part of the kiln. The housing is flared outwardly at the upperand lower parts of the kiln and communicate with chamber 20, 2| ofenlarged section which are also filled with the powdered graphite orother conducting material, the effect of making the chambers of largersection being that the temperature of the graphite therewithin will belower than that of th graphite forming the heating elements proper.

Preferably a pair of chambers 20 and 2| are conducting materialcontained provided for each heating element although, if desired, a pairof such chambers may communicate with two or more than two of theelements and whatever arrangement is adapted each chamber is providedwith an electrode 23 embedded in the powdered graphite therewithin.

In the alternative construction shown in Figure 4 of the drawings, therefractory members I 8 forming the housings for the heating elements areof hollow cylindrical form and, as shown in detail in Figures and 6,each such member comprises an outer tube 24 surrounding an inner tube 25of smaller diameter so as to leave an intervening cavity 26 of hollowcylindrical form which contains refractory powder. Each tube is built upof a plurality of tubular elements placed one upon another, and theupper and lower ends of the refractory housing are flared outwardly tocommunicate with chambers 20 and 2-! as in the preceding construction.

With this construction the vertical pillars l3 are dispensed with andthe cylindrical heating elements are arranged spaced apart in the tworecesses I2 of the kiln.

With both constructions it will be observed that the sides of the upperchamber 20 are wholly, and those of the lower chamber 2| are associatedheating element.

Also in both constructions, the joints between the plates or tubularelements forming the outer wall of the refractory housing are staggeredin relation to those forming the inner wall.

The provision of a powdered refractory filling in the cavity IE or 26 ofthe housing wall ensures that, should any cracks develop in the innerportion I! or tube 25 they will immediately become sealed by the fusedalumina or other similar material.

In addition to applying the invention to a singl tunnel kiln it may beapplied to a multiple tunnel kiln for example as shown in Figure '7wherein the kiln is provided with a pair of spaced tunnels through whichthe goods travel in opposite directions and the two tunnels areseparated by a brickwork wall 21 of substantially zigzag configurationin plan so as to provide adjacent oppositely directed recesses 28 withinwhich are housed heating elements of a form similar to partially, linedby the refractory housing of the that shown in Figures 4 to 6 of thedrawings while the remaining two sides of the tunnels are provided withrecesses 29 similar to the recesses l2 of the construction shown inFigures 1 and 3 and provided with heating elements in the mannerdescribed in connection with that construction.

In using the construction shown in Figure 7 the temperature in adjacenttunnels can be controlled as desired and one tunnel may be Worked at atemperature diiferent from that of an adjacent tunnel.

In addition to applying the invention to tunnel kilns it may be appliedto kilns of the oven chamber type in which case, the heating elementsconstructed as described, may be placed around the sides of the ovenchamber with the narrow dimension of each element wall of the oven.

What we claim then is:

1. An industrial kiln provided with electric resistance heating elementsformed of powdered in refractory housings said refractory housingscomprising inner and outer refractory members spaced at right angles tothe apart to provide a cavitythere-between and refractory powder fillingsaid cavity.

2. An industrial kiln according to claim 1 wherein said refractorypowder comprises fused alumina.

3. An industrial kiln having a heating chamber, said heating chamberhaving a plurality of spaced recesses, electric resistance heatingelements formed of powdered conducting material disposed in each of saidrecesses, refractory members in the form of spaced plates extendingbetween opposite sides of said recesses, said elements being disposedbetween said plates and said recess sides.

4. An industrial kiln having a heating chamber, a plurality of spacedpillars arranged at the side of the heating chamber, electric resistanceheating elements formed of powdered conducting material disposed betweenadjacent pillars, refractory members in the form of spaced platesextending between opposite faces of said pillars, said elements beingdisposed between said plates and said pillar sides.

5. An industrial kiln having a heating chamber, a plurality ofspaced'pillars arrange at the side of the heating chamber, electricresistance heating elements formed of powdered conducting materialdisposed between adjacent pillars, two pairs of refractory platesextending between opposite faces of said pillars, said elements beingdisposed between said pairs of plates and said pillar sides, the platesof each pair being spaced apart to. provide a cavity there-between andrefractory powder filling said cavity.

6. An industrial kiln provided with electric resistance heating elementsformed of powdered conducting material contained in refractory housingscomprising afpair of concentric tubes, the inner and outer tubes beingspaced apart to provide a cavity there-between and refractory powderfilling said cavity.

7. An industrial kiln provided with electric resistance heating elementsof elongated form, formed of powdered conducting material con tained inrefractory housings, opposite ends of said elements communicating withchambers of cross section greater than that of said elements andcontaining powdered conducting material, electrodes in said chambers incontact with the conducting material therein and refractory memberspartially surrounding the conducting material within said chambers.

8. A multiple tunnel kiln comprising a pair of adjacent tunnels, a wallseparating said adjacent tunnels, said Wall being of zigzagconfiguration to provide recesses directed alternately towards one orthe other tunnel and electric resistance heating elements formed ofpowdered conducting material disposed in each of said recesses andcontained in refractory housings.

9. A multiple tunnel kiln comprising a pair of adjacent tunnels, a wallseparating said adjacent tunnels, said wall being of zigzagconfiguration to provide recesses directed alternately towards one orthe other tunnel, electric resistance heating elements formed ofpowdered conducting material disposed in each of said recesses andcontained in refractory housings comprising a pair of concentric tubes,the inner and outer tubes being spaced apart to provide a cavitythere-between and refractory powder filling said cavity. g n

BERNARD J. MOORE. B. C. MOORE.

